Comparison of hand and rotary instrumentation for removing gutta-percha from previously treated curved root canals: a microcomputed tomography study

Efficacy of Reciprocating Instruments in the Removal of Bioceramic and Epoxy Resin-Based Sealers: Micro-CT Analysis

The objective of this study was to evaluate the efficacy of reciprocating instruments in the removal of bioceramic and epoxy resin-based sealers using micro-CT analysis. Root canals of 40 extracted human teeth were instrumented with a size R25 Reciproc instrument. Specimens were randomly divided into two groups (n = 20) according to the root canal filling material. In the first group, root canals were obturated with AH Plus sealer and Reciproc R25 gutta-percha. In the second group, a combination of bioceramic gutta-percha (TotalFill BC) and bioceramic sealer (TotalFill BC) was used. After one week, the retreatment of all specimens was performed using Reciproc instruments. To analyze the differences in the filling remnants, specimens were scanned in a micro-CT device after obturation and after the retreatment procedure. Statistical analysis was performed using the Mann-Whitney U test (p < 0.05). A combination of bioceramic sealer and bioceramic gutta-percha was more effectively removed from canals using a reciprocating instrument, with a filling remnants volume of 4.01 ± 3.13 mm³, in comparison to the combination of epoxy resin-based sealer and gutta-percha (6.96 ± 2.70 mm³) (p < 0.05). A reciprocating instrument was more effective in removing bioceramic sealers than epoxy resin-based sealers, although none of the root canal filling materials were completely removed from the root canals.

Critical analysis of research methods and experimental models to study removal of root filling materials

Despite enjoying high favourable outcome rates, root canal treatment is not always successful. Root canal retreatment is a widely practised option for managing a non-healing root treated tooth. A basic distinction between retreatment and initial treatment is the requirement to remove the existing root filling material occupying the root canal space. Only then, can the technical deficiencies and possible causes of failure be addressed. Hence, the successful removal of the root filling material is critical to achieving the objectives of retreatment. Many different materials and techniques have been used for root canal filling, which have been documented in a plethora of studies; these are mainly laboratory studies investigating the removal of root filling materials. To help guide future research, which may then better inform clinical practice in relation to retreatment procedures, the focus of this narrative review is on the research methods and experimental models employed to study the removal of root filling materials. The current available literature demonstrates great variation in the research methodologies used to study the removal of root filling material, including direct visualization by splitting tooth samples or clearing, three-dimensional radiographic imaging including using microcomputed tomography or cone-beam computed tomography, and a combination of these techniques. Depending on the research method employed, variation also exists in quantification of root filling material removal; these include measurements of surface area, volume or weight, and criteria-based (semi-quantitative) assessment. Experimental models, using human teeth or resin models, differ with respect to standardization techniques and replication of the clinical scenario including initial sample preparation, canal filling, allocation and technical aspects of retreatment procedures. Future models should replicate, as closely as possible, the clinical scenario. Currently, microcomputed tomography provides a highly detailed, non-invasive and non-destructive method of objectively assessing and quantifying root filling removal.

Retrograde Instrumentation of Surgically Resected Roots Using Controlled Memory Files: A Human Cadaver Study

INTRODUCTION

The purpose of this study is to evaluate the amount of residual obturation material of retroinstrumented surgically resected roots using controlled memory files and to evaluate the incidence of adverse treatment outcomes.

METHODS

Thirty maxillary anterior teeth in human cadavers were selected, and nonsurgical root canal treatment was performed on these teeth. A standardized 4-mm osteotomy and a 3-mm root resection with as close to 0° bevel as possible were made on each tooth. A microsurgical diamond tip was used to create a 1- to 2-mm starting point for each retropreparation. A 25/06 and 30/06 VTaper 2H were bent at about 90° angle to mimic the clinical and anatomic restrictions and used to create a retropreparation to a depth of 14 mm. Micro-computed tomography scans were taken and analyzed for volume and percentage of residual obturation material at 5 and 10 mm. In addition, the incidences of instrument separation and crack and ledge formation in the teeth were recorded.

RESULTS

The median volume of residual obturation at 5 and 10 mm was 0.18 mm³ (interquartile range, 0.36 mm³) and 1.97 mm³ (interquartile range, 1.99 mm³), respectively. The overall incidence of file separation during retropreparation was 13.33% (4/30). Among the cases analyzed with micro-computed tomography, none showed crack or ledge formation.

CONCLUSIONS

Retroinstrumentation of surgically resected roots using controlled memory files cleans the canal effectively with relatively low adverse treatment outcomes. Although this novel technique is limited in application, it is a safe and effective way to achieve a deep, clean retropreparation.

Surface deformation of several nickel-titanium rotary instruments after removal of the root canal filling materials: a scanning electron microscope evaluation

The aim of the present study was to investigate and compare the surface deformations of different NiTi rotary files after retreatment under scanning electron microscope (SEM). A total of 240 upper central incisor teeth were obturated with vertical compaction technique and divided into 6 groups. Root canals were retreated by ProTaper Next (PTN), Twisted File Adaptive (TFA), Reciproc (RPC), ProTaper Universal Retreatment (PTR), R-Endo and Mtwo-R NiTi rotary systems. The files investigated under SEM at different magnifications and photomicrographs were captured. The photomicrographs were classified and scored. Kruskal-Wallis and Dunn tests were performed for statistical analyze at 5% significance level. PTR and RPC groups were free of defects like file separation, curving and unwinding but PTN and TFA groups showed 50% file separation. According to the photomicrographs that were captured at high magnification; there were no statistically difference between groups at the coronal thirds of the files (P > 0.05), at the middle third PTN and TFA groups showed statistically more deformation than the other groups (P < 0.05). At the apical third Reciproc was statistically showed less deformation than the other all groups (P < 0.05). Within the limitation of this in vitro study, all NiTi files showed surface deformation in SEM observation after retreatment procedures. There was less deformation in PTR and RPC groups according to other.

The efficacy of retreatment and new reciprocating systems in removing a gutta-percha-based filling material

Objectives

To investigate the efficacy of retreatment and reciprocating rotary systems in removing gutta-percha filling material from root-canal systems.

Methods

A total of 90 single-canal human teeth were instrumented using a F3 ProTaper file and obturated with gutta-percha and the Tubliseal sealer using the lateral-compaction technique. They were divided into five groups according to the rotary system used to remove the filling material: Reciproc, which used the Reciproc-R25 file; WaveOne, which used the WaveOne-Primary file; S1, which used the S1 (25/.06) file; ProTaper-R, which used the ProTaper-Retreatment system; and Mtwo-R, which used the Mtwo®-Retreatment system. The time required to remove the filling material (min) and the associated instrument separation, if any, were recorded. Teeth were cleaved longitudinally and photographed with a high-resolution camera. Images were imported to the AutoCAD application to measure the remaining filling material and the root-canal space. Data were analysed using the one-way analysis of variance and Chi-squared tests.

Results

The Mtwo-R group showed the highest mean remaining filling material (51%) (p < 0.001), with no significant differences among the other groups. The ProTaper group required the least time for filling-material removal (4.95 min), with significant differences compared to the other groups (p < 0.05), except the WaveOne group (5.83 min; p = 1.000). Overall, 13 instruments (15.9%) were used for filling-material removal, with a significantly greater proportion in the Mtwo-R group (33.3%) compared to the other groups (p = 0.009).

Conclusions

Within the limitations of this in vitro study, reciprocating rotary systems were as effective as retreatment rotary systems in removing root-canal filling material. The Mtwo-R system showed the poorest performance with respect to removal effectiveness and instrument separation.

Evaluation of 3 Different Retreatment Techniques in Maxillary Molar Teeth by Using Micro-computed Tomography

INTRODUCTION

Nonsurgical retreatment procedure involves the complete removal of the previous filling material to allow thorough instrumentation, disinfection, and refilling of root canal system. We aimed to determine the residuals of the root-filling material by using 3 different retreatment techniques with the aid of micro-computed tomography.

METHODS

Thirty extracted human maxillary molar teeth were included. All root canals were also obturated with F2 ProTaper single cones and AH Plus sealer. The following retreatment techniques were performed: group 1, ProTaper retreatment files; group 2, Mtwo retreatment files; and group 3, ProFile files. For the assessment of residual filling material, preoperative and postoperative micro-computed tomography scans were compared with each other, and the working time was recorded. One-way analysis of variance was used to analyze the differences between the groups. The significance level was set at P < .05.

RESULTS

None of the retreatment techniques were capable of removing the whole filling material. The percentages of the residual filling materials for groups 1, 2, and 3 were 34.45, 45.43, and 23.63, respectively. There was a statistically significant difference between groups 2 and 3 (P < .05). ProTaper and ProFile instruments required less time for the removal of filling materials when compared with Mtwo instrument.

CONCLUSIONS

ProFile files revealed the best results for endodontic retreatment in terms of both removing capacity and time requirement.

Transportation Assessment in Simulated Curved Canals after preparation with Twisted File Adaptive and BT-Race instruments

Background

This study compared the incidence of deviation along curved canals after preparation with two nickel-titanium (NiTi) rotary systems, Twisted File Adaptive and BT-RaCe.

Material and Methods

Forty resin training blocks with curved canals were filled with ink and divided into two groups according to the instrumentation technique. Preinstrumentation images were acquired by using a stereomicroscope. The canals were up to an instrument #35/0.04. Postinstrumentation images were captured using the same conditions, and the images were superimposed. The amount of resin removed was measured at 8 different points, beginning at the apical terminus of the canal. Differences in the mesial and distal aspects were measured to evaluate the occurrence of deviation. The Student’s-t test was used for comparison of the intragroup deviation. Intergroup analysis was performed by using one-way ANOVA for each level. For multiple comparisons, the Bonferroni test was used and a cutoff for significance was set at 5%.

Results

Intragroup analysis showed that both instrumentation techniques promoted some deviation at all levels. BT-RaCe showed significantly lower deviation at 0 and 4-mm levels than Group Twisted File Adaptive (p<0.05). On the other hand BT-RaCe showed worse performance at level 6.

Conclusions

The results of this study demonstrated that none of the NiTi tested systems was able to instrument curved canals simulated in resin blocks without some deviation during the preparation. There is still need for improvement in the instruments manufacturing aiming the better performance of endodontic files in curved root canals.

Key words:BT-RaCe, Curved root canals, Deviation, Twisted File Adaptive.

Cleanliness of Canal Walls following Gutta-Percha Removal with Hand Files, RaCe and RaCe plus XP-Endo Finisher Instruments: A Photographic in Vitro Analysis

INTRODUCTION

Gutta-percha must be removed from the root canal space during retreatment to ensure a more favorable outcome. The aim of this study was to compare the efficacy of hand instruments, RaCe and RaCe plus XP-endo finisher instruments in removal of gutta-percha from root canal walls during retreatment.

METHODS AND MATERIALS

Thirty single-rooted premolars were prepared, obturated, and divided into three groups according to retreatment method; in group 1, retreatment was carried out by hand instruments, while in groups 2 and 3 retreatment was done using RaCe rotary files alone or accompanied by XP-endo finisher instruments, respectively. After retreatment, teeth were sectioned longitudinally and photographic images were taken. The amount of remaining gutta-percha in coronal, middle and apical thirds was quantified using Image J software. The two-way ANOVA and post hoc Tukey's tests were used to analyze data. The level of significance was set at 0.05.

RESULTS

RaCe cleaned the apical third significantly better than hand instrumentation. In the coronal third, RaCe+XP-endo finisher was more effective than RaCe. RaCe+XP-endo finisher was more effective than hand instrumentation in the entire root canal. The amount of remaining gutta-percha was the least in the apical part and increased toward the coronal part with the use of XP-endo finisher (P<0.05).

CONCLUSION

Rotary instrumentation was more effective in removing gutta-percha from the canal walls. Furthermore, use of XP-endo finisher file resulted in cleaner canal walls and was more effective in removing gutta-percha from the coronal toward the apical part of the canal.

Efficacy of protaper next and protaper universal retreatment systems in removing gutta-percha in curved root canals during root canal retreatment

Purpose:

The aim of this study was to compare the cleanliness of root canal walls after retreatment using ProTaper Next (PTN), ProTaper Universal Retreatment (PTR) nickel-titanium (NiTi) systems and Hedström hand files in curved mesial canals of mandibular molar teeth and the time required for gutta-percha and sealer removal.

Materials and Methods:

Ninety mandibular molar teeth with curved mesial roots were instrumented up to #35.04 with Mtwo NiTi rotary instruments and obturated using the continuous wave of condensation technique. Removal of gutta-percha and sealer was performed using one of the following: PTN and PTR NiTi systems and Hedström hand files. Samples were placed on the VistaScan phosphor plates in the mesio-distal direction and the radiographs were taken. The digital radiographs were analyzed using AutoCAD software. Also, the total time required for gutta-percha removal was calculated by a chronometer.

Results:

The total retreatment time was significantly shorter in the PTN and PTR groups compared with the manual group (p<0.05). There was a significant difference between the groups according to the total residual gutta-percha and sealer (p<0.05). The PTN and PTR groups left significantly less gutta-percha and sealer remnant than the manual group (p<0.001).

Conclusion:

Within the limitations of this study, the PTN and PTR groups showed less residual gutta-percha and sealer than the manual group. The NiTi rotary systems were significantly faster than the manual group in the time required for gutta-percha and sealer removal.

Influence of solvents on the bond strength of resin sealer to intraradicular dentin after retreatment

This study evaluated the removal of filling material with ProTaper Universal Rotary Retreatment system (PTR) combined with solvents and the influence of solvents on the bond strength (PBS) of sealer to intraradicular dentin after canal reobturation. Roots were endodontically treated and distributed to five groups (n = 12). The control group was not retreated. In the four experimental groups, canals were retreated with PTR alone or in combination with xylol, orange oil, and eucalyptol. After filling material removal, two specimens of each group were analysed by SEM and µCT to verify the presence of filling remnants on root canal walls. The other roots were reobturated and sectioned in 1-mm-thick dentin slices that were subjected to the push-out test. Data were analysed by two-way ANOVA and Tukey's test (α = 0.05). SEM and µCT analysis revealed that all retreatment techniques left filling remnants on canal walls. The control group (3.47 ± 1.21) presented significantly higher (p < 0.05) PBS than the experimental groups. The groups retreated with PTR alone (2.59 ± 0.99) or combined with xylol (2.54 ± 0.77) and orange oil (2.32 ± 0.93) presented similar bond strength (p > 0.05), and differed significantly from the group with eucalyptol (1.89 ± 0.63). The solvents reduced the PBS of the sealer to dentin and no retreatment technique promoted complete removal of filling material.

A comparative evaluation of two rotary Ni-Ti instruments in the removal of gutta-percha during retreatment

AIM

The purpose of this study is to achieve an effective method to remove root canal filling material from the root canal system. The study, thus, aims to evaluate the efficacy of the cleaning ability of two different rotary Ni-Ti systems; ProTaper Retreatment files and RaCe System compared to hand instrumentation with Hedstrom files for the removal of gutta-percha during retreatment.

MATERIALS AND METHODS

Thirty mandibular premolars with one single straight canal were decoronated and instrumented with ProTaper files and filled with thermoplastic gutta-percha. After 30 days, the samples were divided into three groups and gutta-percha was removed with the test instruments. The postoperative radiographs were evaluated with known criteria by dividing the root into cervical third, middle third, and apical third. The results were tabulated and Statistical Package for Social Sciences Software (IBM Corporation) was used for analysis.

RESULTS

The mean deviation of the results were first calculated and then t-test and analysis of variance test (two-tailed P value) were evaluated for establishing significant differences. The rotary instruments were effective in removing the gutta-percha from the canals. Therefore, significant difference was observed between the efficacies of the two rotary systems used. The rotary instruments showed effective gutta-percha removal in the cervical and middle one third. (P > 0.05). However, apical debridement was effective with Hedstrom files.

CONCLUSION

The study concluded the use of both rotary and hand instrumentation for effective removal of gutta-percha for retreatment.

Prevention and management of fractured instruments in endodontic treatment

Intracanal instrument fracture is an unpredictable and problematic occurrence that can prevent adequate cleaning and shaping procedures and influence the prognosis of endodontic treatment. The prevalence of instrument fracture is reported to range between 0.28% and 16.2%. This article presents an overview of the prevention and management of instruments fractured during endodontic therapy on the basis of literature retrieved from PubMed and selected journal searches. Instrument fracture occurs because of reduced metal fatigue and/or torsional resistance. The reasons include canal morphology and curvature, manufacturing processes and instrument design, instrument use times and technique, rotational speeds and operator experience. With the development of various equipment and techniques, most of the retained instrument separations can be removed safely. However, in canals without associated periapical disease not every fractured separation should be removed from difficult locations because of the increased risk for root perforation and fracture. In difficult cases, either retain or bypass the fragment in the root canal and ensure regular follow-up reviews. Fractured instruments retained in the presence of periapical disease reduce significantly the prognosis of endodontically treated teeth, indicating a greater need to attempt the removal or bypass of the file separations. Apical surgery might be required in some instances, emphasizing the importance of preventing instrument fracture.

Efficacy of reciprocating and rotary systems for removing root filling material: a micro-computed tomography study

This study aimed to use micro-computed tomography (micro-CT) imaging to evaluate the efficacy of the reciprocating and rotary systems for the removal of root filling materials in comparison with hand files. Thirty maxillary incisor teeth were prepared with ProTaper Universal (PTU) system, filled using cold lateral condensation and randomly divided into three groups of ten teeth each. The root fillings were removed with WaveOne Reciprocating and ProTaper Universal Re-treatment (PTU-R) systems and hand files. Micro-CT was used to scan the specimens before and after each treatment step. Percentage of volume of residual root filling was measured. The operating time was recorded. PTU-R instruments yielded better results for removing filling material, even though there was no statistically significant difference between PTU-R and WaveOne groups. Reciprocating and rotary systems showed similar performances in terms of efficacy and operating time for root filling removal.